1. Field of the Invention
The present invention relates to the coating of pipe and like tubular material, namely the spiral wrapping of a joint of pipe with an elongated continuous web of concrete and more particularly to an improved apparatus for the wrapping of a joint of pipe with a web of concrete. More particularly, the present invention relates to an improved applicator apparatus that continuously spirally wraps the pipe with the web of concrete, the improved applicator including an endless belt, a pair of pulleys, at least one of the pulleys being driven by a motor drive and a gear shaft, and a clutch is positioned outboard of the motor drive/gear box assembly. Even more particularly, the present invention relates to an improved pipe wrapping device that includes an applicator with a belt and pulleys, that can be quickly switched from a driven pulley to an idler pulley at the start of a wrapping of each joint of pipe such as when a rotary pipe conveyor and a belt head assume the rotation of the joint to be wrapped.
2. General Background
In the pipe coating industry, it is well known to spirally wrap a joint of pipe with a reinforced concrete web. Sometimes the web is thick, making the pipe very heavy for underwater installation. Early example of patents that discuss the spiral wrapping of a concrete web about a metal joint of pipe include for example Australian Patent No. 5702/32 dated Aug. 4, 1932 and entitled "PIPE COATING METHOD, MACHINE AND PRODUCT"; U.S. Pat. No. 1,979,656 issued Nov. 6, 1934 entitled "APPARATUS FOR WRAPPING PIPE"; and U.S. Pat. No. 2,037,043 issued Apr. 14, 1936 entitled "PIPE WRAPPING MACHINE". This technology was first commercially developed in about the late 1940's or the early 1950's by Compression Coat of Houston, Tex. Many patents have issued that were assigned to Compression Coat. Examples of compression coat patents include U.S. Pat. Nos. 4,006,049; 4,058,428; and 4,333,783. Each of these patents disclose or contemplate a mixture for mixing aggregate and cement to produce a concrete mass to be formed into a web, a mill for mixing water into the concrete mass, and a pipe conveyor for supporting, advancing and rotating a joint of pipe. This patent also discloses an applicator for wrapping the joint of pipe with a web of concrete, the applicator including an endless belt and a pair of pulleys that support the belt.
Pipe wrapping with concrete is usually accomplished by utilizing an elongated pipe conveyor that supports, advances, and rotates the pipe. A mobile head supports the front end portion of the pipe joint that has already been wrapped in concrete as it leaves an applicator. The applicator for wrapping the joint of pipe with a web of concrete can include an endless belt and a pair of pulleys that support the belt. The concrete web is typically transported to the pipe on the endless belt with a plastic film band placed under the concrete, between the concrete and the belt. Reinforcing wire can be fed from a roll to the endless belt for addition tot he concrete web as reinforcement.
U.S. Pat. Nos. 1,979,656 (issued to N. Whitman in 1934); 2,037,043 (issued to Postlewaite in 1933); 3,740,291 (issued to J. B. Mallard in 1973); 4,006,049 (issued to Garner Feb. 1, 1977); 4,058,428 (issued Nov. 15, 1977 to Case et al.); 4,333,783 issued to Gardner Jun. 8, 1982); and 4,544,426 (issued to Stockman Oct. 1, 1985) all disclose pipe wrapping devices that spirally wrap the pipe with a web of concrete that is fed with an applicator belt to the pipe on a layer of plastic, reinforced with wire. In some of these patents, the plastic film layer and reinforcing wire are fed continuously from a roll (see FIG. 3 of U.S. Pat. No. 4,058,428 and FIG. 1 of U.S. Pat. No. 4,333,783). The Whitman patent 1,979,656 relates to the wrapping of steel pipe with a mortar shell. The method of the Whitman patent includes the step of placing a spiral layer of mortar around the steel pipe and binding the same in place with an outer layer of material which may be fabric or other suitable material such as wire mesh or suitably prepared paper. When the coating process is completed, the binding material becomes a permanent part of the covering and provides the means of holding the mortar in place around the pipe. It also acts as a means of protecting the coating during handling. The Whitman device provides a means of rotatably supporting a section of pipe to be wrapped. A table is movable longitudinally of the pipe. The table having means for applying a preliminary coating of grout to the pipe. The table also having means for supporting a continuous tape arranged to be spirally wound around the pipe over the preliminary coating. The table also allows a layer of mortar to be deposited on the tape before it is wounded around the pipe.
The Postlewaite patent 2,037,043 relates to a machine for wrapping cylindrical objects (such as pipe) with a relatively thick coating of plastic material (such as a bituminous or cementitious mastic) which hardens or sets to form a firm adherent protective layer. The '043 patent is also directed to a method of and a means for applying such plastic material on a continuous tape or band of flexible material which is smoothly and uniformly lapped at the joints between adjacent turns. The machine of the '043 patent includes a shoot disposed at an angle to the pipe and space therefrom, the shoot adapted to guide a flexible tape to be wrapped helically around the pipe by relative motion thereof. Plastic material is supplied onto the tape whereby a continuous coating of appreciable thickness is formed on the pipe beneath the tape.
Australian patent 5702/32 issued in 1931 to Warren Kraner disclosed a process that includes the steps of continuously forming a layer of plastic concrete from a mass and continuously covering the layer away from the mass and continuously wrapping the layer spirally upon a pipe. The layer was formed with a reinforcing strip like wire screening embedded within the strip. The edges of the convolutions applied to the form lapped and then compacted. A strip of surfacing material will simultaneously wound upon the exterior of concrete applied to the pipe form. The Kraner patent also disclosed a means for supporting and rotating a pipe to be coated and a hopper is adapted to receive a mass of concrete. The hopper is adapted to receive a mass of concrete. The hopper included a lower discharge opening for guiding a strip of material like wire screening beneath the opening whereby concrete fed through the opening was distributed upon both sides of the strip. The strip together with the layer of concrete covering both sides of the same was then wound spirally on the pipe.
It is known to drive one of the rollers that support the belt with a chain drive using a motor (for example electric or hydraulic). However, once the applicator and the adjacent joint of pipe are rotated a short distance, the motor drives for the pipe conveyor and for the mobile belt head desirably rotate the pipe and pull the web of concrete from the applicator. If the applicator has a motor drive that drives the powered pulley of the applicator, problems can occur in obtaining an even application of the web.
One of the problems that can occur in the application of the web of material to the pipe is that of rotating the applicator at to high of a speed. This produces a loosening of the plastic web film that supports the concrete. However, another equally troublesome problem is that of powering the applicator pulley at to slow of a speed so that the motor drives of the pipe conveyor and mobile belt head are "pulling" at the web of material thus placing the underlying plastic film intention, stretching it and possibly rupturing it.